Effects of Alcohol

Alcohol is a central nervous system (CNS) depressant. You can think of a depressant as the opposite of a stimulant. It slows down the CNS, thereby slowing brain and nerve function, heart rate, breathing - anything controlled by the central nervous system. Thought processes, emotional responses, and motor coordination are all affected.

  • Slowed reaction time
  • Impaired vision (blurred vision, reduced peripheral vision)
  • Loss of coordination
  • Decreased alertness
  • Impaired judgment

Alcohol disrupts sleep. While a nightcap may help you doze off more quickly, it undermines the quality of your sleep. You don't spend as much time in all-important REM cycles and you tend to wake up too soon.

Since it slows down the CNS, alcohol reduces physiological arousal.  People may report feeling more relaxed, or more interested in sex – but their perceptions are impaired, and their bodies can’t keep up.  Physiological arousal originates in the brain, and depends on proper nerve function. Drinking too much alcohol is a known cause for erectile dysfunction in men.


Excessive drinking both in the form of heavy drinking or binge drinking, is associated with numerous health problems, including:

  • Chronic diseases such as liver cirrhosis (damage to liver cells)
  • Pancreatitis (inflammation of the pancreas)
  • Various cancers, including liver, mouth, throat, larynx (the voice box), and esophagus
  • High blood pressure
  • Psychological disorders
  • Unintentional injuries, such as motor-vehicle traffic crashes, falls, drowning, burns and firearm injuries.

Source: Alcohol and Public Health (

There is no "one size fits all" approach to potential health benefits from alcohol. As little as one drink a day for women has been linked to increased risk for cancer of the breast, liver, rectum, throat, mouth, and esophagus. However, numerous studies dating back decades have shown a positive relationship between moderate alcohol consumption and heart health. 

The benefits for heart health are more prominent in men over 40 and women over 50, and only when consumption is limited to no more than 1 drink a day for women, or 2 drinks a day for men 
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Factors like individual genetics, family history of cancer, family history of heart disease, high blood pressure, cholesterol, and stress level need to be considered to determine if drinking a small amount will end up being harmful or helpful. Experts agree that for people who don't already drink, they should not begin drinking just to gain a small possible benefit. There is no universally "safe" level of drinking other than abstaining (WebMDAlcohol and Your Health).

Standard Serving

A standard serving of alcohol, or "one drink" contains 14 grams (0.5 oz) of pure alcohol (ethanol). 

The amount of alcohol in the drink is more important than the volume of liquid. Different types of drinks contain different concentrations of alcohol. You might see the concentration of alcohol in the drink expressed as a percent (e.g. 40% alcohol by volume), or as a proof. Proof is simply the percentage multiplied x2, so a drink with 40% alcohol by volume is 80 proof. 

Light BeerRegular BeerMicro BrewWhite WineRed Wine80 Proof
4.20% AbV5.00% AbV6.70% AbV12.0% AbV15.0% AbV40.0% AbV
1 drink = 14 oz1 drink = 12 oz1 drink = 9 oz1 drink = 5 oz1 drink = 4 oz1 drink = 1.5 oz
1 bottle = 0.85 drinks1 bottle = 1 drink1 bottle = 1.33 drinks1 glass = 1 drink1 glass = 1 drink1 shot = 1 drink

Blood Alcohol Content

Blood Alcohol Content (BAC) is a measure of alcohol in the blood as a percentage. It is calculated in grams per 100 mL of blood, so a BAC of 0.08 means your blood is 0.08% alcohol by volume.

Using a breathalyzer, BAC is measured as grams per 210 Liters of breath (since the ratio of breath alcohol to blood alcohol is 2,100:1). All the calculations are done inside the device, so the number on the display represents the percentage of alcohol in your blood rather than on your breath. 

The following are typical effects associated with increases in blood alcohol content. Because of the effects of tolerance, some individuals will not experience feelings of relaxation or euphoria until reaching a higher than typical BAC. However, physical and visual effects (e.g. motor skill impairment) are fairly consistent and correspond to the BAC levels indicated. Physical and visual impairments will not improve with increased tolerance. 



  • BAC: Possible Effects
  • .02% to .04%: Lightheaded - Mildly relaxed, mood may be mildly intensified
  • .05% to .07%: Buzzed - Feel warm and relaxed, good moods are better and bad moods are worse, euphoria, may talk louder/act bolder than usual
  • .08% to .10%: Legally Impaired - May slur speech, balance/motor skills become impaired, sight/hearing ability clearly diminished, judgment/self-control impaired, may take poor/risky sexual choices.
  • .11% to .15%: Drunk - "High," balance very impaired, judgment, memory and motor skills impaired, may forget how many drinks you have had past this point, men may have trouble functioning sexually.
  • .16% to .19%: Very Drunk - Euphoria may give way to unpleasant feelings (depression), difficulty talking/walking/standing, sharp increase in chances of physically injuring yourself or others, may experience a blackout at this level or higher, nausea, dizzy, blurred vision.
  • .20%: Confusion and Disorientation - May need help to stand or walk; if you hurt yourself, you probably won't realize it because the alcohol has numbed your pain and your judgment is so impaired you might not do anything about it; nausea and vomiting common, getting very dangerous because gag reflex is impaired, so you could choke if you do throw up (especially if you black out).
  • .35%: Equivalent to general anesthesia, breathing may stop.
  • .40%: Coma likely, breathing and heartbeat slowed to dangerous levels due to slowdown in nerve activity.



Calorie Source

Alcohol itself is a source of calories. The number of calories in a drink is primarily determined by the alcohol content, rather than the amount of sugar that is added to the drink. That's because alcohol is more calorie dense than carbohydrates. 

Alcohol is a source of "empty calories," which means it is calorie dense but does not provide other nutrients, like vitamin and minerals. 

This table shows the relative number of calories (calories per gram) coming from each macro-nutrient group. 

One Gram (g)CarbohydratesProteinAlcoholFats

Alcohol in the bloodstream causes the pituitary gland in the brain to block the creation of vasopressin. This causes the kidneys to send water directly to the bladder rather than reabsorbing filtered water into the bloodstream. This diuretic effect increases as the blood alcohol content increases, and can lead to dehydration - a contributing factor to hangovers. 

Studies have shown that drinking 250 mL of alcoholic beverage causes the body to expel between 800-1000 mL. This means that the body is releasing more than just the liquid being consumed. One way to decrease the effect is to keep your BAC low, and alternate between alcoholic and non-alcoholic drinks (preferably water). 


So which drinks should have the most calories? Drinks with high alcohol content, larger sizes, and additional sugar and syrup mixers. 

Calorie Content of Common Drinks

Normally, we don't think about food in terms of calories per gram. The table below reports the amount of calories in common drinks.  Note: Drink sizes do not necessarily represent Standard Servings. 

Calories Beers
64 Miller Genuine Draft 64 (12 oz)
95 Natural Light (12 oz)
99 Corona Light (12 oz)
110 Bud Light (12 oz)
116 Bud Light Lime (12 oz)
125 Yuengling Lager (12 oz)
150 Heineken (12 oz)
157 Natural Ice (12 oz)
170 Sam Adams Boston Lager (12 oz)
200 Sam Adams Winter Lager (12 oz)
231 Sierra Nevada India Pale Ale (12 oz)
Calories Wine
105 Beringer White Zinfandel (5 oz)
100 Yellow Tail Shiraz (5 oz)
120 Sauvignon Blanc (5 oz)
Calories Malt Beverages
220 Mike's Hard Lemonade (12 oz)
220 Twisted Tea (12 oz)
228 Smirnoff Ice (12 oz)
229 Bacardi Silver Mojito (12 oz)
660 Four Loko (23.5 oz)
Calories Mixed Drinks
409 Bahama Breeze Ultimate Pina Colada (12 oz)
400 Dirty Martini with Olives (6 oz)
425 White Russian (5 oz)
775 Applebee's Mud Slide
780 Long Island (8 oz)

Alcohol is a toxin that must be neutralized or eliminated from the body. Ten percent of alcohol is eliminated through sweat, breath, and urine. Alcohol is volatile (will evaporate in air), so when alcohol in the blood comes in contact with air in the alveoli of the lungs, it can be transferred out of the body through breath.

The liver is the primary organ responsible for the detoxification of alcohol. Liver cells produce the enzyme alcohol dehydrogenase which breaks alcohol into ketones at a rate of about 0.015 g/100mL/hour (reduces BAC by 0.015 per hour). Nothing will speed up the rate of detoxification, but the effective metabolism of alcohol can be limited by medications and liver damage.

When the rate of consumption exceeds the rate of detoxification, BAC will continue to rise.

Once alcohol is swallowed, it is not digested like food. First, a small amount is absorbed directly by the tongue and mucosal lining of the mouth. Once in the stomach, alcohol is absorbed directly into your blood stream through the tissue lining of the stomach and small intestine.

Food in the stomach can inhibit the absorption of alcohol in two ways:

First, it physically obstructs the alcohol from coming in contact with the stomach lining. Food can either absorb alcohol, or simply “take up space” so the alcohol does not enter the bloodstream through contact with the wall of the stomach.

Second, food in the stomach will prevent alcohol from passing into the duodenum, which is the upper portion of the small intestine. The surface area of the small intestine is very large (about the size of a tennis court), so alcohol has more access to enter the bloodstream once it leaves the stomach. If alcohol is sequestered in the stomach it will be absorbed slower.

Once alcohol is in your bloodstream, it is carried to all organs of your body. In the majority of healthy people, blood circulates through the body in 90 seconds, thereby allowing alcohol to affect your brain and all other organs in a short amount of time. The full effects of a drink are felt within 15 to 45 minutes depending on the speed of absorption.

Alcohol enters all tissues of the body except bone and fat. In an adult male, alcohol can penetrate approximately 68% of body tissues. Body composition is important, because if the percentage of adipose tissue is high, the alcohol can only be distributed throughout the remaining lean tissue – resulting in a higher concentration for those areas.

The effects of alcohol on the body will vary according to the individual: their sex, body composition, the amount of alcohol consumed, the presence of food, and the ability of the liver to produce the alcohol dehydrogenase enzymes. 


How Fast Can You Sober Up?

Alcohol leaves the body at an average rate of 0.015 g/100mL/hour, which is the same as reducing your BAC level by 0.015 per hour. For men, this is usually a rate of about one standard drink per hour. However, there are other factors that affect intoxication level (gender, some medications, illness) that will cause BAC to rise more quickly, and fall more slowly. 

Example: At an average rate of -0.015/hr, how long would it take someone with a BAC of 0.20 to sober up?

Time Activity BAC Level
2:00 am In bed, dizzy and disoriented .200
3:00 am Nauseous, unable to sleep .185
4:00 am Very restless .170
5:00 am Sleeping, but not well .155
6:00 am Sleep .140
7:00 am Get up for class with a headache .125
8:00 am Drive to school, risk DUI or worse .110
9:00 am In class, trouble focusing on lecture .095
10:00 am Judgment still impaired .080
11:00 am Mind still fogy, fatigued .065
12:00 pm Not hungry, cottonmouth .050
1:00 pm In afternoon class, still unfocused .035
2:00 pm Head cleaning .020
3:00 pm Feeling a little better .005
4:00 pm Sober at last, but not fully recovered .000

Can You Speed Up This Process?

Once alcohol is in the bloodstream, it can only be eliminated by the enzyme alcohol dehydrogenase, sweat, urine, and breath. Drinking water and sleeping will not speed up the process. Coffee, energy drinks, and a cold shower will not sober you up faster. These might make you feel more awake, but caffeine and cold showers will not pull alcohol out of the blood - and thus will not lower your BAC level.

Tolerance means that after continued drinking, consumption of a constant amount of alcohol produces a lesser effect or increasing amounts of alcohol are necessary to produce the same effect.

Humans develop tolerance when their brain functions adapt to compensate for the disruption caused by alcohol. "Chronic heavy drinkers display functional tolerance when they show few obvious signs of intoxication even at high blood alcohol concentrations (BAC's), which in others would be incapacitating or even fatal"(Chesher & Greeley, 1992).

What's the Difference?

Imagine two people with different levels of tolerance, but the exact same BAC level. How are they different?

  • Better short term memory
  • Ability to hold a conversation
  • Ability to keep eye contact
  • Less intensified moods
  • Better speech, less slurring of words
  • Impaired eye-hand coordination
  • Impaired balance
  • Impaired motor function
  • Decreased peripheral vision


Notice anything? The things that don't improve with tolerance are pretty important for things like driving a car! That's why the legal BAC limit to drive is a set number, and does not depend on whether or not the person has a high tolerance. 

Problems Resulting from High Tolerance

  • Physical damage and impairment are occurring without your knowledge.  With tolerance, you feel less drunk, so you’re less able to accurately judge your ability to function.
  • Your body no longer protects you the way it is meant to – since you’re less likely to vomit or pass out, you may reach even higher, more toxic BAC levels.
  • When you develop tolerance, you can no longer experience the “buzz” – you don’t get the same euphoric effects at low doses.
  • It’s expensive – since you don’t feel the effects as quickly, you end up buying more drinks.
  • Tolerance and withdrawal are the two things that distinguish alcohol abuse from alcohol dependence – if you’re building your tolerance, you’re moving toward physical addiction.

Alcohol poisoning is a condition caused by high concentrations of alcohol in the blood. Blood alcohol concentration rises as alcohol is consumed in large quantities and over short periods of time. 

  • Person cannot be awakened
  • Person has cold, clammy, pale, or bluish skin
  • Person has slow, shallow, or irregular breathing
  • Person is vomiting while passed out and does not wake up

These symptoms are typical of a BAC level in the vicinity of .25-.40.  At that level, the depressant effects of alcohol can simply slow the breathing and heart rate down to a point where a person enters a coma and may die.

However, alcohol can kill before a deadly BAC level is reached. If someone vomits while asleep or passed out, and they are unable to clear their mouth (or if they are asleep on their back), death may occur from asphyxiation. In other words, there is a risk the person could drown on their vomit. This is a risk if the person is drunk enough to vomit, even if they do not have other symptoms of alcohol poisoning.

If You Suspect Alcohol Poisoning...

  • Call 911 if someone shows symptoms of alcohol poisoning
  • Do not leave them alone
  • Do not put them in bed to sleep it off
  • If they pass out, put them on their side to prevent choking on vomit
  • If breathing stops, perform CPR or find someone who knows how

Prevent Alcohol Poisoning in the First Place

It's better to avoid a crisis altogether. Here are some tips to prevent alcohol poisoning in the first place:

  • If you go out with friends, stay together as a group
  • Let someone else know what you are doing and who you are with
  • Set a limit. Before you go out, decide how many drinks you will have.
  • Know the alcohol content and serving size of what you plan to drink.
  • Follow other risk reduction techniques. 

Factors that Affect Intoxication

The more alcohol and/or the shorter the time period, the higher the Blood Alcohol Content (BAC).

Children of an alcoholic are at a greater risk for developing alcoholism – four times greater! This increased risk is sometimes described as a predisposition to alcoholism. Just as we inherit a certain likelihood of heart disease, we are all born with some biological level of risk for alcoholism. For some of us, that risk is increased. Those of us with biological history of alcoholism in our family are at greater biological risk for alcoholism.

Males and females react to alcohol a bit differently. Women tend to be smaller than men. Women get intoxicated faster and stay intoxicated longer. Women have less alcohol dehydrogenase, the enzyme that metabolizes alcohol, so alcohol remains in the bloodstream longer (in fact, men have 40% more than women). Also, women tend to have a higher percentage of body fat, which reduces the percentage of lean body mass that can distribute the concentration of alcohol.

Smaller stature individuals will become impaired quicker. Alcohol can be distributed throughout the body via the circulatory system, and enters most tissues except bone and fat (adipose tissue). This is why body composition is important, because as the percentage of body fat increases, the resulting concentration of alcohol in the lean tissues of the body is proportionally higher.

Carbonation speeds up absorption. Alcohol mixed with carbonated beverages such as Coca-Cola or tonic water will be absorbed more quickly into the bloodstream. This is also true for champagne and wine coolers.

Energy drinks are stimulants and alcohol is a depressant. Energy drinks mask the effects of alcohol by giving you a sense of energy, and the false sense that you are not that intoxicated. Mixing alcohol and energy drinks can cause heart failure because they are opposing stressors on the body’s regulatory systems.

If you are sick or just getting over an illness, you tend to become impaired more quickly.

Marijuana reduces nausea, which can inhibit the body’s ability to remove harmful toxins by vomiting. Marijuana can increase the threshold required to illicit a vomit response.

Strong emotions such as anger, fear, and loneliness tend to hasten impairment. The psychological and social effects of alcohol (and the placebo effects) are also magnified by expectations.

Do not mix alcohol with aspirin, ibuprofen (Advil), or acetaminophen (Tylenol). These drugs are also metabolized by the liver. What you take isn’t the active form, but is transformed in the liver into the active agent. Drinking alcohol while taking painkillers creates a “bottleneck” in the liver. The drug is processed incorrectly, the bi-products kill liver cells, and alcohol is metabolized slower.  It’s also important not to mix alcohol with other depressants, which includes some antihistamines.

Mixing alcohol with prescription drugs often leads to increased or hastened impairment. Alcohol can produce hazardous side effects, reduce heart rate, and drop blood pressure to a dangerous level.

Women who are taking some birth control pills and/or are in the premenstrual time in their cycle may have a higher BAC.

If you lack sleep or are tired, you will become impaired more quickly. If you get five or less hours of sleep for four nights in a row, for example, two drinks will start to feel like six drinks. Another way to describe this: lack of sleep reduces tolerance, so impairment will be experienced at lower BAC levels than normal.

Food in the stomach will slow the absorption of alcohol into the bloodstream and delay impairment. The type of food ingested (carbohydrate, fat, protein) has not been shown to have a measurable influence on BAC. However, we do know that larger the meals, and closer proximity to time of drinking, can lower the peak blood alcohol concentration. This could simply be the result of the food obstructing the alcohol from entering the bloodstream, or because the food will inhibit the stomach from emptying into the small intestine.

There are heritable components of enzyme production that have been identified. Typically, individuals of Asian or Native American descent show reduced levels of alcohol dehydrogenase, meaning that alcohol will remain in the blood longer and high concentrations can build up faster.